Spectromicroscopic measurements of electronic structure variations in atomically thin WSe2

Atomically thin transition metal dichalcogenides (TMDCs) are promising candidates for implementation in next generation semiconducting devices, for which laterally homogeneous behavior is needed. Here, we study the electronic structure of atomically thin exfoliated WSe2, a prototypical TMDC with large spin–orbit coupling, by photoemission electron microscopy, electron energy-loss spectroscopy, and density functional theory. We resolve the inhomogeneities of the doping level by the varying energy positions of the valence band. There appear to be different types of inhomogeneities that respond differently to electron doping, introduced by potassium intercalation. In addition, we find that the doping process itself is more complex than previously anticipated and entails a distinct orbital and thickness dependence that needs to be considered for effective band engineering. In particular, the density of selenium vs tungsten states depends on the doping level, which leads to changes in the optical response beyond increased dielectric screening. Our work gives insight into the inhomogeneity of the electron structure of WSe2 and the effects of electron doping, provides microscopic understanding thereof, and improves the basis for property engineering of 2D materials

Nonlocal dielectric function and nested dark excitons in MoS2

Their exceptional optical properties are a driving force for the persistent interest in atomically thin transition metal dichalcogenides such as MoS2. The optical response is dominated by excitons. Apart from the bright excitons, which directly couple to light, it has been realized that dark excitons, where photon absorption or emission is inhibited by the spin state or momentum mismatch, are decisive for many optical properties. However, in particular the momentum dependence is difficult to assess experimentally and often remains elusive or is investigated by indirect means. Here we study the momentum dependent electronic structure experimentally and theoretically. We use angle-resolved photoemission as a one-particle probe of the occupied valence band structure and electron energy loss spectroscopy as a two-particle probe of electronic transitions across the gap to benchmark a single-particle model of the dielectric function ϵ(q, ω) against momentum dependent experimental measurements. This ansatz captures key aspects of the data surprisingly well. In particular, the energy region where substantial nesting occurs, which is at the origin of the strong light–matter interaction of thin transition metal dichalcogenides and crucial for the prominent C-exciton, is described well and spans a more complex exciton landscape than previously anticipated. Its local maxima in (q≠0,ω) space can be considered as dark excitons and might be relevant for higher order optical processes. Our study may lead to a more complete understanding of the optical properties of atomically thin transition metal dichalcogenides

Artery tertiary lymphoid organs control multi-layered territorialized atherosclerosis B cell responses in aged ApoE-/- mice

Objective: Explore aorta B cell immunity in aged ApoE-/- mice. Approach and Results: Transcript maps, FACS, immunofluorescence analyses, cell transfers, and Ig-ELISPOT assays showed multi-layered atherosclerosis B cell responses in artery tertiary lymphoid organs (ATLOs). Aging-associated aorta B cell-related transcriptomes were identified and transcript atlases revealed highly territorialized B cell responses in ATLOs versus atherosclerotic lesions: ATLOs showed upregulation of bona fide B cell genes including Cd19, Ms4a1 (Cd20), Cd79a/b, and Ighm though intima plaques preferentially expressed molecules involved in non-B effector responses towards B cell-derived mediators, i.e. Fcgr3 (Cd16), Fcer1g (Cd23), and the C1q family. ATLOs promoted B cell recruitment. ATLO B-2 B cells included naïve, transitional, follicular, germinal center, switched IgG1+, IgA+, and IgE+ memory cells, plasmablasts, and long-lived plasma cells (PCs). ATLOs recruited large numbers of B-1 cells whose subtypes were skewed towards IL-10+ B-1b cells versus IL-10- B-1a cells. ATLO B-1 cells and PCs constitutively produced IgM and IgG and a fraction of PCs expressed IL-10. Moreover, ApoE-/- mice showed increased germinal center B cells in renal lymph nodes, IgM-producing PCs in the bone marrow, and higher IgM and anti-MDA-LDL IgG serum titers. Conclusions: ATLOs orchestrate dichotomic, territorialized, and multi-layered B cell responses in the diseased aorta; germinal center reactions indicate generation of autoimmune B cells within the diseased arterial wall during aging

Electric-Field Gradient at Cd Impurities in In2o3. A FLAPW Study

We report an ab initio study of the electric-field gradient tensor (EFG) at Cd impurities located at both inequivalent cationic sites in the semiconductor In2O3. Calculations were performed with the FLAPW method, that allows us to treat the electronic structure of the doped system and the atomic relaxations introduced by the impurities in the host lattice in a fully self-consistent way. From our results for the EFG (in excellent agreement with the experiments), it is clear that the problem of the EFG at impurities in In2O3 cannot be described by the point-charge model and antishielding factors.Comment: 4 pages, 2 figures, and 2 table

Development of coordination and muscular fitness in children and adolescents with parent-reported ADHD in the German longitudinal MoMo Study

This study examined the development of muscular fitness and coordination in children and adolescents with and without attention deficit hyperactivity disorder (ADHD) over a period of 11 years. Data was collected in three measurement waves as part of the longitudinal, representative Motorik-Modul (MoMo) study in Germany (2003–2006, 2009–2012, 2014–2017). The overall sample comprised 2988 participants (253 with ADHD, 65% males; 2735 non-ADHD, 47% males; mean age 9 years). Structural equation modeling was conducted, and the estimated models had a good fit. No differences in muscular fitness were observed between participants with and without ADHD. Participants with ADHD had a lower coordinative performance at first measurement than those without ADHD. The difference in coordinative performance persisted throughout the study period

The Physical Basis for Long-lived Electronic Coherence in Photosynthetic Light Harvesting Systems

The physical basis for observed long-lived electronic coherence in photosynthetic light-harvesting systems is identified using an analytically soluble model. Three physical features are found to be responsible for their long coherence lifetimes: i) the small energy gap between excitonic states, ii) the small ratio of the energy gap to the coupling between excitonic states, and iii) the fact that the molecular characteristics place the system in an effective low temperature regime, even at ambient conditions. Using this approach, we obtain decoherence times for a dimer model with FMO parameters of $\approx$ 160 fs at 77 K and $\approx$ 80 fs at 277 K. As such, significant oscillations are found to persist for 600 fs and 300 fs, respectively, in accord with the experiment and with previous computations. Similar good agreement is found for PC645 at room temperature, with oscillations persisting for 400 fs. The analytic expressions obtained provide direct insight into the parameter dependence of the decoherence time scales.Comment: 5 figures; J. Phys. Chem. Lett. (2011

Limited Macrophage Positional Dynamics in Progressing or Regressing Murine Atherosclerotic PlaquesBrief Report

Objective Macrophages play important roles in the pathogenesis of atherosclerosis, but their dynamics within plaques remain obscure. We aimed to quantify macrophage positional dynamics within progressing and regressing atherosclerotic plaques. Approach and Results In a stable intravital preparation, large asymmetrical foamy macrophages in the intima of carotid artery plaques were sessile, but smaller rounded cells nearer plaque margins, possibly newly recruited monocytes, mobilized laterally along plaque borders. Thus, to test macrophage dynamics in plaques over a longer period of time in progressing and regressing disease, we quantified displacement of nondegradable phagocytic particles within macrophages for up to 6 weeks. In progressing plaques, macrophage-associated particles appeared to mobilize to deeper layers in plaque, whereas in regressing plaques, the label was persistently located near the lumen. By measuring the distance of the particles from the floor of the plaque, we discovered that particles remained at the same distance from the floor regardless of plaque progression or regression. The apparent deeper penetration of labeled cells in progressing conditions could be attributed to monocyte recruitment that generated new superficial layers of macrophages over the labeled phagocytes. Conclusion: s Although there may be individual exceptions, as a population, newly differentiated macrophages fail to penetrate significantly deeper than the limited depth they reside on initial entry, regardless of plaque progression, or regression. These limited dynamics may prevent macrophages from escaping areas with unfavorable conditions (such as hypoxia) and pose a challenge for newly recruited macrophages to clear debris through efferocytosis deep within plaque